CHRA/turbine bolts relaxing.
#164
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Now it's my turn to be confused and please correct me whereever I am wrong. You (and Savington?) are currently using stainless bolts, safety wired. The bolts are stretching (not turning out) due to heat expansion and loss of tensile strength at elevated temps, beyond the tensile limit, causing the CHRA to become loose inside the turbine housing and allowing the turbine blades to eat themselves into the turbine housing. This is the problem we are trying to solve, right or no?
If yes, right, then how is vibration the main reason for the stainless bolts stretching, instead of the fact that they are about as strong as a wet noodle at the temps the turbine sees and that even on the smoothest engine the same thing might happen eventually just due to the weight of a turbo hanging off the 6mm bolts? Plus, stainless does grow more than other materials when heated theoretically requiring a higher tightening torque to maintain clamping force as temps rise, assuming you are below the tensile limit for the bolt @ temp (which we aren't due to the vibration forces and perhaps just the weight of the turbo itself). Wouldn't the solution be bolts that are significantly stronger at turbine temps that are either safety wired or held with a tab plate so they don't vibrate loose? I'm sure the vibrations don't help at all but other things on your engine that are less hot aren't vibrating apart. (flawed logic?)
In my perhaps completely wrong mind, you can: 1. cool the studs down (tials new watercooled turbine for watercraft), 2. use stronger bolts at high temps (tial supplied inconel bolts), 3. keep the compressor/CHRA from vibrating to the point that the assembly does not load the stainless bolts beyond their yield point & stay stretched (unknown solution...some crazyass voodoo crane). 4. switch to a different setup (T2 flange with trackspeed inconel studs) 5. use larger diameter bolts (possibly room for retapping for 8mm? stainless is still the wrong material regardless of size) 6. Combo of the above. What's easier/cheaper? #3 doesn't seem the easiest to me
If yes, right, then how is vibration the main reason for the stainless bolts stretching, instead of the fact that they are about as strong as a wet noodle at the temps the turbine sees and that even on the smoothest engine the same thing might happen eventually just due to the weight of a turbo hanging off the 6mm bolts? Plus, stainless does grow more than other materials when heated theoretically requiring a higher tightening torque to maintain clamping force as temps rise, assuming you are below the tensile limit for the bolt @ temp (which we aren't due to the vibration forces and perhaps just the weight of the turbo itself). Wouldn't the solution be bolts that are significantly stronger at turbine temps that are either safety wired or held with a tab plate so they don't vibrate loose? I'm sure the vibrations don't help at all but other things on your engine that are less hot aren't vibrating apart. (flawed logic?)
In my perhaps completely wrong mind, you can: 1. cool the studs down (tials new watercooled turbine for watercraft), 2. use stronger bolts at high temps (tial supplied inconel bolts), 3. keep the compressor/CHRA from vibrating to the point that the assembly does not load the stainless bolts beyond their yield point & stay stretched (unknown solution...some crazyass voodoo crane). 4. switch to a different setup (T2 flange with trackspeed inconel studs) 5. use larger diameter bolts (possibly room for retapping for 8mm? stainless is still the wrong material regardless of size) 6. Combo of the above. What's easier/cheaper? #3 doesn't seem the easiest to me
Last edited by TurboTim; 02-24-2011 at 10:43 PM.
#172
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www.mcmaster.com
Item numbers:
1421T61
1661T27
8870A27
4370A6
1257A74
9529K53
EDIT: Oops, safety first!
54185T601
54315T18
5450T13
Last edited by TurboTim; 02-24-2011 at 03:01 PM.
#178
Tour de Franzia
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PT doesn't have anyone driving hard enough to kill hardware
PT doesn't think you will drive hard enough to kill hardware
PT turbo won't tell you if they do
PT won't give you consideration.
I'll test the Inco bolts for you. Then you can get the EDM "drilled" and life successfully through my misfortunes.